Industrial vehicles, such as mining trucks and locomotives, with electric or hybrid drive systems often include large components, such as motors and alternators, that generate a substantial amount of heat. These components may be cooled using blower motors or other cooling mechanisms designed to help dissipate heat.
Motors are often protected by fuses that are designed to prevent damage to the motors due to a current surge. A fuse is typically provided on each input power line; a motor powered by a three-phase power source has three incoming power lines that are each protected by a separate fuse. When a fuse is damaged or blown, the fuse prevents current from traveling to the motor on the line to which the fuse is coupled. This causes a single phasing condition in the motor in which the motor is no longer powered by three-phase input power. Single phasing of the motor can cause a high current condition in the motor, for example, when a motor is activated from a stopped position.
U.S. Pat. No. 3,742,303 (“the '303 patent”) of Dageford, which issued on Jun. 26, 1973, discloses a system that detects a single phasing condition and discontinues the supply of voltage to a compressor motor in the event of single phasing. The system of the '303 patent includes two current transformers connected to the three-phase power supply. The first transformer monitors current on one phase of the three-phase line, and the second transformer monitors current on another phase of the three-phase line. The output of the current transformers is sent to current sensors, and the output of the current sensors and a temperature sensor is used to control a switch. The switch controls operation of a magnetic contactor configured to discontinue supply of power to the compressor motor.
Conventional motor protection systems monitor one or more phases of an input power line of a motor and directly trigger mechanical devices to cut off power to the motor in the event that single phasing is detected. Such systems typically can only respond to a single phasing condition by discontinuing power to the motor being protected; they may not be capable of providing information about the single-phasing condition to a user and/or controlling operation of other systems or devices that may be affected by the motor being shut down. Such motor protection systems may not be configured to separately monitor current on all three phases of a three-phase input power line.
The motor protection systems of the present disclosure solve one or more problems set forth above and/or other problems of the prior art.